This invention relates to a device for controlling the operation of a system for heating a building.
Known devices in the field of the invention, usually described as "programmed controllers", typically include a time clock which is used to start and stop a heating appliance which forms part of a system for heating a building. In the simplest case, the heating appliance is controlled by its own thermostat and by thermostats fitted, for example, to radiators installed in various rooms of the building. An improvement on such a system includes the use of "inside" and "outside" thermostats for controlling the appliance with regard to the weather. For example, more heat needs to be generated on cold days than on warm days. However, the time clock will still provide "start" and "stop" signals in accordance with a preset program and this can result in either insufficient heating in a building at the start of a cold day, or a waste of heat on a warm day when, for example, the temperature of the building reaches a comfortable level long before the building is occupied.
British Pat. No. 1,193,711 to Honeywell relates to "control of a thermal conditioning system". It mentions that prior computer systems "have not proved completely successful and are, of course, quite expensive". In the described system signals representing inside and outside temperatures appear to be directly fed to a Wheatstone bridge system, without predetermined proportioning. In U.S. Pat. Nos. 2,832,870 and 3,076,606 the morning warm-up period may be varied in duration, depending upon outside temperature. Other systems to vary the duration of the morning warm-up period are found in U.S. Pat. Nos. 2,778,571; 2,719,672 and 2,583,397. The present invention presents advantages, in terms of cost, accuracy or reliability, compared to the control systems of the above-named patents.